Obese women who undergo bariatric surgery before having a baby have a much lower risk of developing serious health problems during pregnancy, finds a study published in the British Medical Journal today.

Obesity, especially extreme obesity, is a risk factor for hypertensive disorders in pregnancy. These include serious conditions such as pre-eclampsia, where abnormally high blood pressure and other disturbances develop during pregnancy. They are a common cause of pregnancy complications and infant death and affect about 7% of all pregnancies in the United States.

Bariatric surgery is an effective weight loss intervention for women with a body mass index (BMI) of 40 or more, or a BMI of 35-40 with associated conditions like diabetes. But little is known about the impact of surgery on hypertensive disorders in pregnancy.

So researchers from Johns Hopkins University in the United States set out to test the theory that women who had a delivery after bariatric surgery would have lower rates of hypertensive disorders in pregnancy compared with women who had a delivery before surgery.

Using insurance data from 2002-2006, they identified 585 obese women aged 16-45 years who had undergone bariatric surgery, had at least one pregnancy and delivery, and had continuous medical insurance coverage during pregnancy plus two weeks after delivery.

Of these women, 269 had surgery before delivery and 316 had surgery after delivery.

Compared with women who delivered before surgery, women who delivered after surgery had substantially lower rates (75%) of hypertensive disorders, even after adjusting for factors such as age at delivery, multiple pregnancy, surgical procedure, pre-existing diabetes, and insurance plan.

These results have important clinical, public health, and policy implications, say the authors. For example, bariatric surgery could be considered in women of childbearing age who wish to start a family, and have a BMI of 40 or more, or a BMI of 35-40 with associated conditions.

Future research should also address long term maternal and child health after pregnancies and deliveries following bariatric surgery in terms of weight management, nutritional status, and burden of long term chronic disease, they conclude.